I. Field of the Invention
The present invention relates to accessories for light aircraft, and in particular to a unique and highly efficient design for a wing-mounted doorstop for limiting the opening of the aircraft door. Various embodiments of the invention include the capabilities of generating smoke for illustrating the laminar flow of air over the aircraft wing, for acting as a radar reflector, and for automatically folding from an extended position to a position of lower drag resistance.
II. Description of the Prior Art
Aircraft manufacturers have commonly included a door-stopping mechanism within the hinge of doors installed on light aircraft. These hinges are typically satisfactory for normal operation, but prove highly unsatisfactory during heavy commercial or training utilization. Also, during conditions of inclement weather any high-speed winds coming from the aft section of the aircraft will tend to cause the door to act as a sail and to automatically open. It is not unusual for the force of these winds to completely break or disengage the normal door limit device. When this failure mode occurs, the door continues its rotation on its hinges until the external doorknob or opening mechanism communicates with a section of the fuselage adjacent the engine cowling. Typically the doorknob or opening mechanism is completely thrust through or at least severely dents the sheet metal of the engine cowling. Repair of these damages often exceeds $100 to the aircraft fuselage and $20 for the repair of the door hinge. It is also not unusual for the same incident to recur shortly after the repairs have been completed, since the repairs do not eliminate the original problem, but instead merely correct the symptoms of the problem.
The present inventor is the owner and manager of a fixed base operation which employs a large number of low-wing aircraft which are utilized for the instruction of student pilots. After several years of continuous repairs to the fleet of light aircraft, and after repeatedly repairing the same damage to the same aircraft, the present inventor recognized the design faults of the hinge-positioned doorstop and further recognized that an outboard doorstop would be required. The present invention has conducted an extensive search of presently available devices for satisfying these requirements, but has been unable to discover any satisfactory devices or solutions. The present inventor has also conducted a search for previously patented devices which would provide a solution to this problem, and the following references are provided as illustrative of the devices located.
U.S. Pat. Nos. Des. 86,677 issued to Johnson and 194,451 issued to Morgan disclose designs for doorstops of the types utilized in homes and offices for limiting the angular opening of typical wooden or metal doors. Both of these designs utilize heavy construction and bulky elements which are not suitable for use on aircraft since the size and design of the doorstops would significantly increase the drag and disturb the laminar flow of air over the wing when the aircraft is flying.
Hagstrom, in U.S. Pat. No. 2,432,150, discloses a normal doorstop which includes a movable head which is pivoted about an angular rotational face. The head is adapted to engage the opening door in a variety of different physical orientations. Taylor, in U.S. Pat. No. 2,454,414, discloses another doorstop which includes at one end thereof a screw-type device for being fastened to the wall and includes at the other end thereof a suction cup which is movably mounted to the frame of the doorstop in order to allow the suction cup to pivot for communicating normally with the door.
In addition to the above references the inventor has also located and examined the following U.S. patents which were deemed to add little if anything to the previously discussed references: U.S. Pat. Nos. 2,682,683, 2,809,061, 2,189,048, 2,121,766, 1,044,412, 890,701.
The above references were located in the following classes/subclasses (among others): 244/129.4, 129.5; 16/82, 83, 84, 86R, 86A, and 49; 292/238; and D8/402.